I don't use k9, so just a thought. You might have to disable push email from the email settings online. Not sure what email your using but that might help.
Are you getting K9 mail notifications or notifications from the native email app ? check settings in both
Are you using POP3, or IMAP? If you use IMAP, and you have PUSH folders, those messages get pushed real time.
Check Account Settings -> Fetching Email -> Push Folders. Try setting to NONE.
on my wifes droid she gets a notification every single time she gets an email. i have the settings for all her email accounts set to only poll once every 3 hours, and yet she gets every single email pushed to her. any suggestions?
So i looked last night and its pop3 not imap. And the push settings are greyed out and off. Its weird. I even put her droid side by side with my X and our settings are exactly the same. So weird.Are you using POP3, or IMAP? If you use IMAP, and you have PUSH folders, those messages get pushed real time.
Check Account Settings -> Fetching Email -> Push Folders. Try setting to NONE.
Are both accounts POP? What servers are specified for Yahoo?